HPV Vaccine Exceeds Expectations by Providing Herd Immunity

A new study shows the human papillomavirus (HPV) vaccine is far more effective than expected, with benefits extending beyond those who receive the vaccine. Specifically, the study showed vaccination not only reduces rates of HPV infection and the presence of precancerous cells in the cervix in people who receive the vaccine, it also reduces rates of HPV-related diseases in people who are not vaccinated.

The study, which expanded upon a 2015 meta-analysis that looked at the real-world effects of the vaccine, included a total of 65 studies that spanned eight years and included more than 60 million people living in 14 countries. Each study measured either changes in the number of new HPV infections, genital warts diagnoses or cases of abnormal cells associated with cervical cancer in countries before and after they adopted routine HPV vaccination in girls. (Two countries included in the analysis, the U.S. and Australia, also recommend the vaccine for boys.)

Researchers found there was a significant decrease in the prevalence of two strains of HPV that cause 70 percent of cervical cancers, HPV 16 and 18. In addition, there was a decrease in the prevalence of precancerous cells in the cervix, which can develop into cancer. In countries where at least half the population actually received the vaccine, researchers saw evidence of herd immunity, meaning there was a decrease in the prevalence of HPV-related diseases even among those who weren’t vaccinated since vaccination leads to fewer HPV hosts. They also saw a decrease in genital warts diagnoses among unvaccinated boys and older women. And, among girls within the age groups targeted for vaccination, there were fewer diagnoses of three HPV strains that the vaccine does not specifically protect against, a phenomenon called cross-protection. Countries in which people in multiple age groups received the vaccine also saw a greater decrease in HPV-related disease.

“The impact of the HPV vaccination has actually exceeded expectations,” said Lauri Markowitz, associate director of science for HPV at the Centers for Disease Control and Prevention, who worked on the study. “The trials showed that HPV vaccines are very effective, and data from the real world has confirmed that.”